Pep Guardiola has been subjected to a scathing personal attack by Bayern Munich's first-team doctor, who has described the Spaniard as a "person with a low self-esteem who will do everything to hide it from others".
Hans-Wilhelm Muller-Wohlfahrt, who has treated a number of high-profile athletes throughout his career including Usain Bolt, Darren Gough and Paula Radcliffe, had worked at Bayern for more than 35 years by the time Guardiola was appointed as head coach in 2013.
The 75-year-old left the Bundesliga club after 38 years in the wake of a 3-1 Champions League quarter-final first-leg defeat away to Porto in April 2015 that he claims Guardiola blamed him for and which proved the tipping point in their troubled relationship.
Having since returned to Bayern, the doctor has now launched a scathing attack on Guardiola, even taking a shot at the coach's personality and state of mind, in his new autobiography.
"I consider Pep Guardiola a person with a low self-esteem, who will do everything to hide it from others," Muller-Wohlfahrt said in his book, Seeing With Your Hands: My Life And My Medicine, serialised in Bild.
"Because of that he seems to live in a constant fear. Not so much of defeats but of the loss of power and authority.
"He knew everything better: Five minutes warm-up had to be enough. But that couldn't end up well. Apparently he saw me as a receiver of commands whom he could order every time he wants."
Guardiola left Bayern at the end of the 2015-16 season and took the reins at Manchester City.